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Journal ArticleDOI

Confinement and heating of plasmas in the JET Tokamak

01 Dec 1986-Plasma Physics and Controlled Fusion (IOP Publishing)-Vol. 28, pp 1943-1954

Abstract: The JET Tokamak has been operated in a wide variety of conditions The results highlight the problem of confinement degradation Several measures are planned to reduce or overcome this effect
Topics: Magnetic confinement fusion (63%), Tokamak (54%), Jet (fluid) (54%)

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Plasma Physics and Controlled Fusion
Confinement and heating of plasmas in the JET
Tokamak
To cite this article: A Ainsworth 1986 Plasma Phys. Control. Fusion 28 1943
View the article online for updates and enhancements.
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Confinement and
heating
of
plasmas
in
the
JET
Tokamak
1915
INTRODUCTION
Table
1
___

1946
R.
J.
BICKEKTOY
and
the
JET TEAM
Poloidal
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,
I
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10
15
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25
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40
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Fig.
1
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Poloidal
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Plasma current
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I
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Abstract: A wide range of studies on JET have contributed greatly to the development of the ELMy H-mode as a high-performance scenario for fusion devices and to the understanding of the physical processes that underlie it. Development has focused on the production of a high-performance, high-density, stationary scenario suited to deuterium-tritium operation and with small edge energy loads. Physics studies have made strong progress in the understanding of the L-H threshold, energy confinement, pedestal physics, and edge-localized mode behavior. A strong focus of this work has been providing a basis for extrapolation to future machines, such as ITER, for which, as the largest existing tokamak, JET has been of particular importance.

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Abstract: Electron heating during ICRH in the JET tokamak is studied. Electron heating profiles are obtained by measuring the increase in electron temperature after sawtooth crashes. By studying the increase in electron heating during power ramp-up it is possible to distinguish direct electron heating from indirect electron heating via minority ions. For direct electron heating, power deposition profiles are obtained. For indirect electron heating, the time dependence is consistent with classical slowing-down of high energy ions on electrons through Coulomb collisions.

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Abstract: In this paper, minority regime fast‐wave ICRF (Ion cyclotron range of frequency) heating experiments conducted on the Alcator C tokamak [Nucl. Fusion 26, 1665 (1986)] are described. Up to 450 kW of rf (radio frequency) power at frequency f=180 MHz was injected into plasmas composed of deuterium majority and hydrogen minority ion species at magnetic fields of B0≂12 T, densities 0.8≤ne≤5×1020 m−3, and minority concentrations 0.25≲ηH≤8%. Typical ion temperatures were TD(0)∼1 keV, while, depending on density, typical electron temperatures were in the range Te(0)∼1.5–2.5 keV. Central deuterium ion temperature increases of ΔTD(0)=400 eV were observed at ne=1×1020 m−3, while significantly smaller ion temperature increases were observed at higher densities. At the highest densities, ion heating became insignificant due in part to a limitation on power handling by the antenna that became more severe with increasing density. Significant electron heating was not observed at any density. Heating of the minority spe...

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References
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Journal ArticleDOI
Robert James Goldston1Institutions (1)
Abstract: Recent results from confinement scaling experiments on tokamaks with ohmic and strong auxiliary heating are reviewed. An attempt is made to draw these results together into a low-density ohmic confinement scaling law, and a scaling law for confinement with auxiliary heating. The auxiliary heating confinement law may also serve to explain the saturation in tau/sub E/ vs anti n/sub e/ observed in some ohmic heating density scaling experiments.

398 citations


Journal ArticleDOI
R.J. Bickerton, R. Behrisch1, J. Ehrenberg1Institutions (1)
Abstract: JET tokamak performance has been progressively raised, culminating in operation at the full design level of 5 MA plasma current in a toroidal field at 3.4 T. the plasma current, position, shape and line-average electron density are controlled by feed-back systems. By glow discharge cleaning in H2/methane mixtures, the interior of the vessel has been coated with carbon. This reduces the fraction of power radiated

32 citations


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P.P. Lallia, JET-Team, J. Ehrenberg1, H. Jaeckel1  +5 moreInstitutions (1)
Abstract: Heating the JET plasma well above temperatures reached in the ohmic phase is the aim of the two additional heating systems planned for JET: ion cyclotron resonance heating (ICRF) and neutral beam injection (NBI) Operations with the latter started in February 1986, initially with hydrogen injection, up to a power level of 7 MW ICRF power has been delivered to the plasma by three antennae and has reached power levels of 6 MW for 2 s In most experiments, the frequency of the waves is adjusted to position the minority ion resonance layer close to the centre of the discharge, resulting in a centrally peaked power deposition profile Results have also shown that the increase of the volume averaged electron temperature was much less dependent on the radial position of the ion resonance layer than were the central temperatures of both ions and electrons which can both approach 5 keV In cases of 'on axis' heating, large increases in the sawtooth activity is observed with sawtooth periods exceeding 03 s Initial results with NBI have shown a decrease of the global energy confinement time with additional power similar to the one observed with ICRF heating

14 citations


Journal ArticleDOI
G Duesing1Institutions (1)
Abstract: A long pulse ( approximately 10 s) neutral beam injector with eight beam sources and one integrated beam-line system has been taken into operation on JET. The sources are arranged in two vertical groups. H0 beams were injected into D+ plasmas with particle energies (in the full energy fraction) of

12 citations


Journal ArticleDOI
Abstract: Presents an overview of the main results obtained on JET. The author deals with the measures to control the impurity contamination and the resulting wall and limiter conditions. The impurity situation during ohmic discharges is reviewed and the main effects resulting from auxiliary heating are given.

8 citations


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